They are fully 32bit with antialiasing and 8bit transparency. The icon dimensions range from: 256x256, 48x48, 32x32, 24x24 and 16x16.
The format is not the new Vista PNG icon format, but the ordinary uncompressed (non PNG) BMP format (that can be converted easily to Vista icon format with appropriate application, which will gain around ~60% space due to the PNG compression).
The icons are not unique, that is, you may find the same icons that you have bought in other applications.
The price is €10 10 icons, so you can choose the single icons you like and order them by quantity, or you can buy the whole package for €250, and get all the icons cheaper.

3delite's Icon Free Set.zip1MB - 35+ with various quality icons.
Some are big as 256x256 with 32bit transparency and antialiasing, some are only 16x16.
Don't know which of them is copyrighted and which is not, if any.